| reflowing on that model is not a good thing.
you are experiencing returns on amd or intel model? or both?
if you use jovy machine for the work, absolutely avoid pre programmed thermal profiles... they don't let you to set a very important parameter, the TAL (time above liquid) , if the tal is too short, as in the pre programmed profile, the solder joint will not be reliable.
and also, the thermal ramp is gotta be adeguate, if the temp raises up less than 1,5 centigrade per second, the solder joint will be unreliable too.
and last but not least... i suggest you to use only new bga chip from factory.
why ?
i've done many researc, and in many cases, in the nvidia chips, the defective part is the flip chip itself . The flip chip is the little square at the center of the whole bga.
the flip chip is bonded with the substrate (the green part of the whole chip) exactly like a bga... yes, it has under itself many hard alloy spheres, about 200 micron diameter....
when you do reballing or reflow you are going to heat this small connections too, so, the chip will work for that reason... and even if you do a perfect rebballing and soldering on the board, thi chip will fail in the future cause the problem are not the balls between bga and board( second level connection) but are the small connection between the flip chip and the substrate(first level connection)
many times the problem is this, other time the problem is the second level connection, but it is impossible to figure wich kind of fault are, so replacing the chip with a new one it is the best deal. |